Exhaust muffler



L. M. MORRISH EXHAUST MUFFL Filed Jan. 20,

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ATTORNEY United States Patent 2,985,252 EXHAUST MUFFLER Leonard M. Morrish and Lloyd E. Muller, Flint, Mich., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Jan. 20, 1955, Ser. No. 482,996

3 Claims. (Cl. 181-56) This invention relates to muifiers for engines employed in motor vehicles and has particular relation to mufi lers for multicylinder engines having two or more rows of cylinders and in which it is desirable to provide two or more exhaust conduits leading from the rear of the vehicle.

improved operation may be obtained from internal combustion engines in motor vehicles when exhaust conduits of adequate size are employed. However, in the construction of motor vehicles of recent design and employing engines of larger capacity it has become diflicult to find enough room to provide a single exhaust conduit of adequate size. It is, therefore, desirable, particularly when V type engines having two rows of cylinders are employed, to provide dual exhaust systems. This makes it possible to employ two exhaust conduits of about the size of the single exhaust conduit previously employed.

Also, in the construction of larger and wider passenger automobiles of present design and in which relatively larger interiors are provided, it has become more difiicult to find space for the mufilers required, particularly when dual exhaust systems are employed.

Space has been found to be available extending transversely of the vehicle and behind the rear seat and above and at the rear of the rear axle of the vehicle. However, this space does not etficiently provide room for two mufliers when dual exhaust systems are provided. A single mufiier for a dual exhaust system which can be located in this space has not heretofore been considered practical.

It is now proposed to provide a single mtifiler for a dual exhaust system that can be located transversely of of the motor vehicle, which will accommodate the two banks of cylinders of a V type engine and which will provide two exhaust conduits leading from the mufller to the rear of the vehicle in locations where space may be available for such conduits.

When single mufi'lers are provided for each exhaust conduit of a dual exhaust system the problem of attenuating the sounds in the exhaust gases resulting from operation of the engine is greater than when a single exhaust system has been provided. This is because the sounds resulting from the operation of a single bank of cylinders of a V type engine are of lower frequency than if the two banks were connected together and a single muffier employed. in an 8 cylinder engine, for example, in one instance it is necessary to silence the sounds involved in the operation of what amounts to two engines of four cylinders. In the other instance, the problem involved is the silencing of sounds involved in one 8 cylinder engine.

In the present instance it is proposed to provide a single mufiler for silencing both banks of cylinders of a V type engine. The cylinder banks may be connected within the muffler or elsewhere if this is desirable.

In the drawing:

Figure 1 is a cross sectional view of a mufller and part of the exhaust system adapted to be employed in silencing the sounds involved in the operation of a V type or other engine having multiple rows of cylinders and employed in a motor vehicle or elsewhere.

Figures 2 and 3 are fragmentary views illustrating louvers that may be employed in the interior structure of the mufller.

Referring particularly to Figure 1 the mufiier 10 comprises an outer casing 11 of circular, oval or other configuration and having casing ends indicated at 12. The space within the casing 11 is divided by partitions 13, 14, 16, 17 and 18 into compartments 19, 21, 22, 23, 24 and 26., The compartment 24 may be considered an inlet compartment into which the exhaust gas from two rows of cylinders of an engine may be discharged byone or more conduits. In the present instance it is proposed to employ a single large exhaust conduit 27 which is adapted to receive exhaust gas from the two rows of cylinders of a V type or other engine and to discharge the exhaust gas into the compartment 24. This may be done by having the conduit 27 connected to the casing 11 in such a way as to communicate with a centrally disposed inlet compartment 24. The end of the conduit 27 may project into the compartment 24 and may be secured therein by bracket means 28, which is welded or otherwise secured to the casing 11. From the compartment 24 the exhaust gas may flow into the compartment 22 through a conduit 29 extending through the walls 16 and 17 and the compartment 23. From the compartment 22 the exhaust gas may flow in opposite directions from the mufiier 10 through outlet conduits indicated at 31 and 32. The conduit 31 is secured in openings in one of the casing ends 12 and in the partitions 13 and 14. The conduit 32 is secured in the other of the ends 12 of the casing 11 and the partitions 18, 17 and 16. The'partitions 13, 14, 16 and 17 are arranged to provide compartments 21 and 23 of substantially equal resonant capacity and of large volume. The end 12 and the partition 13 and the end 12 and the partition 18 are also arranged to provide compartments 19 and 26 of substantially equal resonant capacity and of smaller volume than the compartments 21 and 23. The compartments 21 and 23 form large resonating chambers connected to the conduits 31 and 32, respectively, by couplings indicated at 33.

The couplings 33 are passages formed by a multiplicity of louvers or projections 34 formed in the conduits 31 and 32 in such a way that the sound waves within the conduits will extend into the resonating chambers 21 and 23. Individual openings forming louvers 34 are formed in any suitable manner as by forming slits in the conduits 31 and 32 in the areas indicated by the dotted lines surrounding the louvers and by projecting the material of the conduits outwardly as is indicated in Figures 2 and 3.

The compartments 19 and 26 also form smaller resonating chambers which are connected to the conduits 31 and 32, respectively, by similar louvers indicated at 36 and involving the use of the projections 34. The conduits 31 and 32 also may be connected to other such smaller pairs of resonating chambers indicated at 37 and 38. The resonating chambers 37 and 38 may be of substantially equal size and may be formed by tubes 39 spaced about the conduits 31 and 32 and secured thereto by flanged rings 41. One of the tubes 39 may be secured in the partition 14, the other in the partitions 17 and 18. The resonating chambers 37 and 38 may also be connected to the conduits 31 and 32 by louvers indicated at 42 and involving the use of the projections 34.

Exhaust gas from the engine may enter the chamber 24 through conduit 27 and flow to chamber 22 through conduit 29. The chambers 22 and 24 act as expansion chambers for the gas and provide walls by which sound waves are reflected in all directions. This results in the 33 absorption of sound by the chambers by interference between the sound waves of different frequencies.

The chambers 22 and 24 also serve as capacitances between which conduit 29 acts as an impedance to provide a low pass filter in series with the outlet conduits 31 and 32. The low pass filter tends to pass sounds of low frequency to the conduits 31 and 32 and to attenuate the higher frequency sounds. In the conduits 31 and 32 the sounds which are passed by the low pass filter tend to be attenuated in the pairs of resonating chambers 21 and 23, 19 and 26, and 37 and 38. The chambers 21 and 23 are tuned through the couplings 33 to the sounds of low frequency within the conduits 31 and 32, the resonating chambers 19 and 26 are tuned through couplings 36 to sounds of higher frequency and the pairs of resonating chambers 37 and 38 are tuned through couplings 42 to the sounds of highest frequency.

It will be apparent that the mufiier structure provides a pair of series of resonating chambers tuned to different frequences of sound, this pair being in parallel relation and in series with a low pass filter.

The exhaust gas is discharged from the conduits 31 and 32 toward the rear of the vehicle with which the mufiler may be employed and on opposite sides of the vehicle through bends 44.

We claim:

1. A muffler for attenuating the sound of a fluid flow comprising, a tubular casing having first and second end walls, a plurality of transverse partitions in said casing forming a plurality of longitudinally spaced chambers, an inlet tube in fluid connection with a first of said chambers adjacent said first end wall, an imperfor-ate tube fluidly connecting said first chamber and a second of said chambers spaced therefrom, a first outlet tube in fluid connection with said second chamber and said first end wall, a third chamber between said second chamber and said second end wall, a second outlet tube in fluid connection with said second chamber and said second end wall, a first acoustical coupling means connetcing said second outlet tube with said third chamber, a fourth chamber between said first and said second chambers, and a second acoustical coupling means connecting said first outlet tube and said fourth chamber.

2. The muffier of claim 1 further comprising first and second imperrorate tubular members spaced radially outward of a portion of said first. and said second outlet tubes respectively forming a fifth chamber between said first imperforate member and said first outlet tube and a sixth chamber between said second imperforate member and said second outlet tube, acoustical coupling means connecting said first outlet tube with said fifth chamber, and acoustical coupling means connecting said second outlet tube with said sixth chamber.

3. The mufller defined by claim 1 wherein said imperforate tube and said second outlet tube are transversely spaced and longitudinally overlap.

References Cited in the file of this patent UNITED STATES PATENTS 674,210 Loomis May 14, 1901 794,226 Ihrig et al July 11, 1905 951,770 Miller Mar. 8, 1910 1,688,995 Smith Oct. 23, 1928 1,692,317 Stewart Nov. 20, 1928 2,065,232 MacKenzie et a]. Dec. 22, 1936 2,078,754 Day Apr. 27, 1937 2,103,810 Caspar Dec. 28, 1937 2,151,470 Hollerith Mar. 21, 1939 2,175,410 Powell Oct. 10, 1939 2,184,891 Bourne Dec. 26, 1939 2,193,791 Hollerith et a1 Mar. 19, 1940 2,213,614 Scarritt Sept. 3, 1940 2,247,746 Burt July 1, 1941 2,337,299 Noblitt et al Dec. 21, 1943 2,357,791 Powers Sept. 5, 1944 2,573,474 Marx Oct. 30, 1951 2,692,025 Maxim Oct. 19, 1954 FOREIGN PATENTS 817,517 France May 24, 1937 

